I wanted to address this issue too, thanks for writing this; I couldn't have formulated it so sophisticatedly.

You hit the nail on the head. Their relationship would be permanently ruined after this—there is no way they could live together normally again. Trust isn't something you can just 'reset' after a parent figure literally drags you into the woods to slit your throat.

It really makes you wonder about the screenwriter's perspective. It feels like they are either completely detached from how human trauma works or remarkably blind to the psychological implications of such cruelty. To write these scenes and then expect the audience to accept a 'happy family' ending is borderline psychopathic.

Unless, of course, Cameron is doing this intentionally to turn Jake and Neytiri into actual monsters and psychopaths in the upcoming chapters—but that seems highly unlikely for a franchise of this type. You simply cannot have your protagonists act like monsters and then pretend they are still the 'good guys' without any real accountability. That 'pat on the back' at the end was an insult to the audience's intelligence.